Collision mitigation and avoidance

ABSTRACT

A system includes a computer including a processor and a memory, the memory storing instructions executable by the processor to, upon determining a front threat number exceeds a threat threshold, determine a rear time to collision between a turning host vehicle and a target, and, upon determining that the rear time to collision is below a time threshold, actuate a component based on a rear threat number for the target.

BACKGROUND

Vehicle collisions often occur at intersections. Collision mitigationbetween a host vehicle and a target may be difficult and expensive toimplement. For example, determining a threat assessment for the targetmay use limited or inaccurate data to assign excessive risk to ascenario that in fact may not require avoidance or mitigation.Furthermore, performing the threat assessment may result in positiveidentifications of threat that may not require mitigation, which can beoperationally costly for a vehicle computer and vehicle components,increasing processing cycles of the vehicle computer to perform thethreat assessment and actuate the vehicle components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example system for operating a vehiclein an intersection.

FIG. 2 is a view of an example host vehicle.

FIG. 3 is a view of the example host vehicle interacting with an exampletarget.

FIG. 4 is a view of the example host vehicle missing the example target.

FIG. 5 is a view of the example host vehicle operating according to arear point of the example target.

FIG. 6 is a view of the example host vehicle moving beyond the rearpoint of the example target.

FIG. 7 is a block diagram of an example process for operating the hostvehicle during a turn.

DETAILED DESCRIPTION

A system includes a computer including a processor and a memory, thememory storing instructions executable by the processor to, upondetermining a front threat number exceeds a threat threshold, determinea rear time to collision between a turning host vehicle and a target,and, upon determining that the rear time to collision is below a timethreshold, actuate a component based on a rear threat number for thetarget.

The instructions can further include instructions to determine anoverall threat number based on the rear threat number and the frontthreat number.

The overall threat number can be based on a threat multiplier that isbased on the rear threat number.

The instructions can further include instructions to set the threatmultiplier to zero when the rear threat number is below a rear threatthreshold.

The instructions can further include instructions to determine the frontthreat number based on a front point of the target and the rear threatnumber based on a rear point of the target.

The instructions can further include instructions to determine the rearthreat number when a predicted lateral distance from the host vehicle toa rear corner of the target is below a distance threshold.

The instructions can further include instructions to determine the reartime to collision when the front threat number exceeds the threatthreshold for a first time in a turn.

The rear threat number can be a brake threat number.

The instructions can further include instructions to actuate a steeringcomponent to complete a turn when the rear threat number is below a rearthreat threshold.

The instructions can further include instructions to determine the reartime to collision based on a predicted rear longitudinal distance.

A method includes, upon determining a front threat number exceeds athreat threshold, determining a rear time to collision between a turninghost vehicle and a target, and, upon determining that the rear time tocollision is below a time threshold, actuating a component based on arear threat number for the target.

The method can further include determining a threat multiplier based onthe rear threat number.

The method can further include setting the threat multiplier to 0 whenthe rear threat number is below a rear threat threshold.

The method can further include determining the front threat number basedon a front point of the target and the rear threat number based on arear point of the target.

The method can further include determining the rear time to collisionwhen the front threat number exceeds the threat threshold for a firsttime in a turn.

A system includes a brake, a steering component, means for determining arear time to collision between a turning host vehicle and a target upondetermining a front threat number exceeds a threat threshold, and meansfor upon actuating one of the brake or the steering component based on arear threat number for the target upon determining that the rear time tocollision is below a time threshold.

The system can further include means for determining a threat multiplierbased on the rear threat number.

The system can further include means for setting the threat multiplierto 0 when the rear threat number is below a rear threat threshold.

The system can further include means for determining the front threatnumber based on a front point of the target and the rear threat numberbased on a rear point of the target.

The system can further include means for determining the rear time tocollision when the front threat number exceeds the threat threshold fora first time in a turn.

Further disclosed is a computing device programmed to execute any of theabove method steps. Yet further disclosed is a vehicle comprising thecomputing device. Yet further disclosed is a computer program product,comprising a computer readable medium storing instructions executable bya computer processor, to execute any of the above method steps.

Determining a time to collision, a lateral distance, and a threat numberbased on a rear point of a target provides collision avoidance andmitigation for front impacts, side impacts, and false positives for aturning host vehicle. The computer in the vehicle can provide brakingduring front-front impacts in an OnComing Turn Across Path (OCTAP)scenario and during front-side impacts during an OCTAP scenario. Thecomputer in the vehicle can prevent braking during “near miss”scenarios, i.e., false positive indications of a collision based on afront point and a rear point of the target where the vehicle will passby the rear end of the target during the turn. Thus, the computerprovides braking functionality for different host front impact OCTAPscenarios and utilizes multiple points of information about the targetto more accurately avoid and mitigate collisions. The computer accountsfor impact potential at the side of the target while still accountingfor front-front impact prevention.

FIG. 1 illustrates an example system 100 for operating a vehicle 101 inan intersection. The system 100 includes a computer 105. The computer105, typically included in a vehicle 101, is programmed to receivecollected data 115 from one or more sensors 110. For example, vehicle101 data 115 may include a location of the vehicle 101, data about anenvironment around a vehicle 101, data about an object outside thevehicle such as another vehicle, etc. A vehicle 101 location istypically provided in a conventional form, e.g., geo-coordinates such aslatitude and longitude coordinates obtained via a navigation system thatuses the Global Positioning System (GPS). Further examples of data 115can include measurements of vehicle 101 systems and components, e.g., avehicle 101 velocity, a vehicle 101 trajectory, etc.

The computer 105 is generally programmed for communications on a vehicle101 network, e.g., including a conventional vehicle 101 communicationsbus. Via the network, bus, and/or other wired or wireless mechanisms(e.g., a wired or wireless local area network in the vehicle 101), thecomputer 105 may transmit messages to various devices in a vehicle 101and/or receive messages from the various devices, e.g., controllers,actuators, sensors, etc., including sensors 110. Alternatively oradditionally, in cases where the computer 105 actually comprisesmultiple devices, the vehicle network may be used for communicationsbetween devices represented as the computer 105 in this disclosure. Inaddition, the computer 105 may be programmed for communicating with thenetwork 125, which, as described below, may include various wired and/orwireless networking technologies, e.g., cellular, Bluetooth®, Bluetooth®Low Energy (BLE), wired and/or wireless packet networks, etc.

The data store 106 can be of any type, e.g., hard disk drives, solidstate drives, servers, or any volatile or non-volatile media. The datastore 106 can store the collected data 115 sent from the sensors 110.

Sensors 110 can include a variety of devices. For example, variouscontrollers in a vehicle 101 may operate as sensors 110 to provide data115 via the vehicle 101 network or bus, e.g., data 115 relating tovehicle speed, acceleration, position, subsystem and/or componentstatus, etc. Further, other sensors 110 could include cameras, motiondetectors, etc., i.e., sensors 110 to provide data 115 for evaluating aposition of a component, evaluating a slope of a roadway, etc. Thesensors 110 could, without limitation, also include short range radar,long range radar, LIDAR, and/or ultrasonic transducers.

Collected data 115 can include a variety of data collected in a vehicle101. Examples of collected data 115 are provided above, and moreover,data 115 are generally collected using one or more sensors 110, and mayadditionally include data calculated therefrom in the computer 105,and/or at the server 130. In general, collected data 115 may include anydata that may be gathered by the sensors 110 and/or computed from suchdata.

The vehicle 101 can include a plurality of vehicle components 120. Inthis context, each vehicle component 120 includes one or more hardwarecomponents adapted to perform a mechanical function or operation—such asmoving the vehicle 101, slowing or stopping the vehicle 101, steeringthe vehicle 101, etc. Non-limiting examples of components 120 include apropulsion component (that includes, e.g., an internal combustion engineand/or an electric motor, etc.), a transmission component, a steeringcomponent (e.g., that may include one or more of a steering wheel, asteering rack, etc.), a brake component (as described below), a parkassist component, an adaptive cruise control component, an adaptivesteering component, a movable seat, or the like.

When the computer 105 partially or fully operates the vehicle 101, thevehicle 101 is an “autonomous” vehicle 101. For purposes of thisdisclosure, the term “autonomous vehicle” is used to refer to a vehicle101 operating in a fully autonomous mode. A fully autonomous mode isdefined as one in which each of vehicle 101 propulsion (typically via apowertrain including an electric motor and/or internal combustionengine), braking, and steering are controlled by the computer 105. Asemi-autonomous mode is one in which at least one of vehicle 101propulsion (typically via a powertrain including an electric motorand/or internal combustion engine), braking, and steering are controlledat least partly by the computer 105 as opposed to a human operator. In anon-autonomous mode, i.e., a manual mode, the vehicle 101 propulsion,braking, and steering are controlled by the human operator.

The system 100 can further include a network 125 connected to a server130 and a data store 135. The computer 105 can further be programmed tocommunicate with one or more remote sites such as the server 130, viathe network 125, such remote site possibly including a data store 135.The network 125 represents one or more mechanisms by which a vehiclecomputer 105 may communicate with a remote server 130. Accordingly, thenetwork 125 can be one or more of various wired or wirelesscommunication mechanisms, including any desired combination of wired(e.g., cable and fiber) and/or wireless (e.g., cellular, wireless,satellite, microwave, and radio frequency) communication mechanisms andany desired network topology (or topologies when multiple communicationmechanisms are utilized). Exemplary communication networks includewireless communication networks (e.g., using Bluetooth®, Bluetooth® LowEnergy (BLE), IEEE 802.11, vehicle-to-vehicle (V2V) such as DedicatedShort Range Communications (DSRC), etc.), local area networks (LAN)and/or wide area networks (WAN), including the Internet, providing datacommunication services.

FIG. 2 illustrates an example host vehicle 101. The computer 105 in thevehicle 101 defines a coordinate system, e.g., a two-dimensionalrectangular coordinate system. The coordinate system defines alongitudinal direction X and a lateral direction Y and an origin at apoint O on a center point of a front bumper of the host vehicle 101. Thelongitudinal direction X is a vehicle-forward direction, i.e., thedirection in which a propulsion 120 moves the vehicle 101 when asteering component 120 is at a neutral position. The lateral direction Yis perpendicular to the longitudinal direction X. The host vehicle 101has a length H_(length), i.e., a distance measure of the host vehicle101 in the longitudinal direction X, and a width H_(width), i.e., adistance measure of the host vehicle 101 in the lateral direction Y.

The computer 105 can determine a speed V and an acceleration a for eachof the host vehicle 101 and the target 300. The speed V is the vectorchange in position in the coordinate system and can be subdivided intoV_(long), i.e., the speed in the longitudinal direction X, and V_(lat),i.e., the speed in the lateral direction Y. The acceleration a is thetime rate of change of the speed V, and can be subdivided into along,i.e., the acceleration in the longitudinal direction X, and a_(lat),i.e., the acceleration in the lateral direction Y. The computer 105 candetermine the speed V and the acceleration a based on data 115 collectedfrom the sensors 110.

The computer 105 can determine a yaw angle ψ and a yaw rate {dot over(ψ)} for the host vehicle 101. The yaw angle ψ is the angle definedbetween the trajectory 200 of the host vehicle 101 and the longitudinalaxis X. That is, the yaw angle ψ and yaw rate {dot over (ψ)} representmotion of the host vehicle 101 in a turn.

FIG. 3 illustrates the host vehicle 101 and a target 300 in anintersection. As used herein an “intersection” is defined as a locationwhere two or more vehicles' current or potential future trajectoriescross. Thus, an intersection could be at any location on a surface wheretwo or more vehicles could collide, e.g. a road, a driveway, a parkinglot, an entrance to a public road, driving paths, etc. Accordingly, anintersection is determined by identifying an area where two or morevehicles may meet, i.e., collide. The size of the area defining theintersection can be specified to encompass an area in which collisionsmay occur, e.g., based on a number of roadway lanes, a roadway lanesize, a vehicle size, location data of prior collisions, etc. Forexample, the intersection can encompass 400 m² to account for themeeting of two adjacent roadway lanes and two transverse roadway lanes.Such determination uses potential future trajectories of a host vehicle101 as well as nearby other vehicles and/or other objects.

The host vehicle 101 can perform a “turn.” As used herein, a “turn” is apath along which the host vehicle 101 travels from a current roadwaylane to a transverse roadway lane. For example, the host vehicle 101 canperform a turn into a roadway lane perpendicular to a current roadwaylane, i.e., a left turn or a right turn. As the host vehicle 101performs a turn, the host vehicle 101 may collide with the target 300.For example, in an OnComing Turn-Across Path (OCTAP) scenario, the hostvehicle 101 turns across a predicted path of the target 300 in anadjacent roadway lane. FIG. 3 illustrates an example front-sidecollision, i.e., the predicted trajectory 200 of the host vehicle 101means a prediction that a front end of the host vehicle 101 will collidewith a side of the target 300.

As used herein, the subscript “h” refers to the host vehicle 101, andthe subscript “tg” refers to the target 300. For example, V_(h) is thespeed of the host vehicle 101 and V_(tg) is the speed of the target 300.

To determine a likelihood of a collision between the host vehicle 101and the target 300, the computer 105 can determine a “threat number” forthe target. As used herein, a “threat number” is a scalar value between0 and 1 that the computer 105 can use to determine whether a specifictarget 300 will intersect or collide with the host vehicle 101.Specifically, the computer 105 may determine the acceleration threatnumber ATN, the brake threat number BTN, and the steering threat numberSTN for the host vehicle 101 and the target 300, and based on the threatnumbers ATN, BTN, STN, which may be combined into a single overallthreat number TN, actuate components 120 of the host vehicle 101.

The BTN is a measure of a needed longitudinal deceleration to allow thehost vehicle 101 to stop or reduce speed before colliding with thetarget 300. The BTN can be based on a measured host vehicle 101 speed, adistance between the target 300 and the host vehicle 101, and therespective projected trajectories of the target 300 and the host vehicle101. The computer 105 can determine a longitudinal deceleration to stopor reduce speed of the host vehicle 101 before colliding with the target300, e.g., 2 m/s². The computer 105 can determine a maximum decelerationof the host vehicle 101, e.g., 8 m/s². The BTN can be the ratio of theneeded deceleration to the maximum deceleration, e.g., BTN=2/8=0.25. Ifthe needed deceleration to avoid a collision with the target 300 exceedsthe maximum deceleration of the host vehicle 101, i.e., BTN>1, then thecomputer 105 can set the value of the BTN to 1, i.e., if BTN>1, BTN=1.

The STN is a measure of a needed lateral acceleration to allow the hostvehicle 101 to steer away from the target 200. As with the BTN, thecomputer 105 can determine a needed lateral acceleration to avoid acollision between the host vehicle 101 and the target 300. The STN canbe the ratio of the needed lateral acceleration to a maximum lateralacceleration of the host vehicle 101. If the needed lateral accelerationexceeds the maximum lateral acceleration, the computer 105 can set theSTN to 1.

The ATN is a measure of a needed longitudinal acceleration to allow thehost vehicle 101 to accelerate and pass the target 300. As describedabove for the BTN and the STN, the computer 105 can determine a neededacceleration to allow the host vehicle 101 to pass the target 300 and amaximum available acceleration of the host vehicle 101. The ATN can bethe ratio of the needed longitudinal acceleration to the maximumlongitudinal acceleration of the host vehicle 101. If the neededlongitudinal acceleration exceeds a maximum longitudinal acceleration,the computer 105 can set the ATN to 1. The computer 105 may determinethe STN, BTN, and/or ATN to produce a respective overall threat numberTN for the target 300.

The computer 105 can actuate one or more vehicle components 120 based onone of the threat numbers exceeding a predetermined threat threshold.The threat threshold can be determined based on, e.g., empirical testingof vehicles 101 in intersections, simulation modeling of vehicles 101,brake capacity, steering limits, etc. For example, if the overall threatnumber TN is above a threat threshold of 0.7, the computer 105 canactuate a brake 120 to decelerate the host vehicle 101, e.g., to −6.5meters per second squared (m/s²). In another example, if the threatnumber is above 0.4 but less than or equal to 0.7, the computer 105 canactuate the brake 120 to, e.g., a deceleration of −2.0 m/s². In anotherexample, if the threat number is greater than 0.2 but less than or equalto 0.4, the computer 105 can display a visual warning on a vehicle 101HMI and/or play an audio warning over a speaker.

The computer 105 can determine the threat number based on a specificposition or location in the coordinate system representing a point onthe exterior surface of the target 300. That is, the threat numberpredicts a probability or likelihood that the host vehicle 101 willcollide with a specific point on the target 300. As shown in FIG. 3, thespecific point may be a front point 305, i.e., a coordinate pointrepresenting a portion of a front bumper of the target 300. The computer105 thus determines a “front threat number,” i.e., a prediction ofwhether the host vehicle 101 will collide with the front point 305 ofthe target 300. The computer 105 can determine the front point 305 basedon data 115 collected by the sensors 110 detecting the target 300. Forexample, the front point 305 may be a center point of the front bumperof the target 300, as shown in FIG. 3. When the front threat numberexceeds a front threat threshold, determined based on, e.g., empiricalimpact tests, impact simulations, etc., the computer 105 can actuate oneor more components 120 to avoid and/or mitigate a collision with thetarget 300.

The computer 105 can determine a rear point 310 of the target 300, i.e.,a coordinate point representing a portion of a rear bumper of the target300. For example, the rear point 310 may be a corner of the rear bumperof the target 300 closest to the host vehicle 101. The computer 105 candetermine a “rear threat number” TN_(rear), i.e., a prediction ofwhether the host vehicle 101 will collide with the rear point 310 of thetarget 300. For example, the rear threat number TN_(rear) can be a rearbrake threat number BTN_(rear), i.e., a brake threat number based on therear point 310 of the target 300. The computer 105 can determine therear point 310 based on data 115 collected by the sensors 110 detectingthe target 300. The computer 105 can determine the rear threat numberTN_(rear) upon determining that the front threat number TN_(front)exceeds the front threat threshold. When the rear threat number exceedsa rear threat threshold, determined based on, e.g., empirical impacttests, impact simulations, etc., the computer 105 can actuate one ormore components 120 to avoid and/or mitigate a collision with the target300.

The computer 105 can determine a relative distance L between the hostvehicle 101 and the target 300. The “relative distance” is thestraight-line distance between a predetermined point on the host vehicle101 and a predetermined point on the target 300. The predetermined pointon the host vehicle 101 can be the origin O of the coordinate system.The predetermined point on the target 300 can be the front point 305,the rear point 310, or another point for which the computer 105determines to calculate the relative distance L. For example, therelative distance L between the origin O of the host vehicle 101 and thefront point 305 of the target 300 can be a “front distance” L_(front).In another example, the relative distance L between the origin O of thehost vehicle 101 and the rear point 310 of the target 300 can be a “reardistance” L_(rear). The computer 105 can further decompose the relativedistance L into a “longitudinal distance” L_(long), i.e., a relativedistance in the longitudinal direction, and a “lateral distance”L_(lat), i.e., a relative distance in the lateral direction.

The computer 105 can determine a rear longitudinal distanceL_(rear,long) at a time period T after a current time t according to afourth-order polynomial Taylor expansion of kinematic equations of thehost vehicle 101 and the target 300 as follows:

$\begin{matrix}{{L_{{rear},{long}}\left( {t + T} \right)} = {{L_{{rear},{long}}(t)} + \frac{{a_{{long},h}(t)}{{\overset{.}{\psi}}_{h}(t)}^{2}T^{4}}{8} + \frac{{V_{{long},h}(t)}{{\overset{.}{\psi}}_{h}(t)}^{2}T^{3}}{6} + {\frac{1}{2}\left( {{a_{{long},{tg}}(t)} - {a_{{long},h}(t)}} \right)T^{2}} + {\left( {{V_{{long},{tg}}(t)} - {V_{{long},h}(t)}} \right)T}}} & (1)\end{matrix}$where a_(long,h) is the longitudinal acceleration of the host vehicle101, a_(long,tg) is the longitudinal acceleration of the target 300,V_(long,h) is the longitudinal speed of the host vehicle 101,V_(long,tg) is the longitudinal speed of the target 300, and {dot over(ψ)}_(h) is the yaw rate of the host vehicle 101.

The computer 105 can determine a rear lateral distance L_(rear,lat) at atime period T after a current time t according to a fourth-orderpolynomial Taylor expansion of kinematic equations of the host vehicle101 and the target 300 as follows:

$\begin{matrix}{{L_{{rear},{long}}\left( {t + T} \right)} = {{L_{{rear},{lat}}(t)} - \frac{{V_{{long},h}(t)}{{\overset{.}{\psi}}_{h}(t)}^{3}T^{4}}{24} + \frac{{a_{{long},h}(t)}{{\overset{.}{\psi}}_{h}(t)}T^{3}}{3} + {\frac{1}{2}\left( {{a_{{lat},{tg}}(t)} - {a_{{lat},h}(t)}} \right)T^{2}} + {\left( {{V_{{lat},{tg}}(t)} - {V_{{lat},h}(t)}} \right)T}}} & (2)\end{matrix}$where a_(lat,h) is the lateral acceleration of the host vehicle 101,a_(lat,tg) is the lateral acceleration of the target 300, V_(lat,h) isthe lateral speed of the host vehicle 101, and V_(lat,tg) is the lateralspeed of the target 300.

FIG. 4 illustrates a “near miss” scenario for the host vehicle 101 andthe target 300. As used herein, a “near miss” is when the front threatnumber is above a front threat threshold and the rear threat number isbelow a rear threat threshold. As described above, the computer 105 candetermine the rear threat number upon determining that the front threatnumber exceeds the front threat threshold. The front threat thresholdcan be, e.g., 0.7. The rear threat threshold can be, e.g., 0.6. That is,the “near miss” occurs when the predicted trajectory 200 of the hostvehicle 101 indicates that the host vehicle 101 would move behind thetarget 300 without colliding with the target 300 but the computer 105determines, based on the front threat number alone, that a collision islikely. To prevent unnecessary braking during the near miss, thecomputer 105 determines the rear threat number and determines whether tobrake the vehicle 101 based on the rear threat number. As describedbelow, the computer 105 can determine, when the front threat numberexceeds the front threat threshold, whether a collision with the rearpoint 310 is likely. Alternatively or additionally, the vehicle 101 canmiss the target 300 while the computer 105 determines that a collisionis likely when, e.g., the computer 105 detects only the rear point 310of the target 300, the target 300 has a length between the front point305 and the rear point 310 that is substantially shorter than a distancebetween the host vehicle 101 and the target 300, etc.

FIG. 5 illustrates the computer 105 detecting a side collision betweenthe host vehicle 101 and the target 300 based on the rear point 310. Asdescribed above for FIGS. 3-4, during the turn, the computer 105 candetermine, based on the front point 305 and the predicted trajectory200, a front threat number indicating whether the host vehicle 101 islikely to collide with the target 300. To determine whether this frontthreat number indicates a false positive, the computer 105 can identifythe rear point 310 of the target 300 and a rear threat number, e.g., arear brake threat number BTN_(rear), as described above. FIG. 5illustrates that the rear threat number would indicate a collision, andthe computer 105 can actuate components 120 to avoid and/or mitigate thecollision.

FIG. 6 illustrates the computer 105 detecting a near miss between thehost vehicle 101 and the target 300 based on the rear point 310. Asdescribed above, in a near miss scenario, the computer 105 determines afront threat number TN_(front) that would indicate a likely collisionwith the target 300 but the predicted trajectory 200 of the host vehicle101 would move the host vehicle 101 to pass the rear end of the target300. That is, the near miss is a false positive indication of acollision with the target 300, and the computer 105 can preventcollision mitigation and avoidance to allow the host vehicle 101 to movepast the target 300.

To adjust the overall threat number TN based on data 115 collected aboutthe rear point 310, the computer 105 can determine a threat multiplier.As described below, the computer 105 can determine the threat multiplierbased on the front threat number TN_(front) and the rear threat numberTN_(rear). As used herein, the “threat multiplier” is a numerical valuethat is multiplied to the front threat number TN_(front) to determinethe overall threat number TN. For example, the threat multiplier may be0 (e.g., in a near miss) to indicate that the host vehicle 101 is notlikely to collide with the target 300 even when the front threat numberTN_(front) indicates otherwise. Alternatively, the threat multiplier maybe 1 (e.g., if a rear time to collision, as discussed below, is below apredetermined time threshold) to indicate that the host vehicle 101 islikely to collide with the target 300. Yet further alternatively, thethreat multiplier may be a different number to account for theadditional or lower risk of collision based on data 115 about the rearpoint 310 of the target 300, e.g., a number between 0 and 1. That is,the threat multiplier between 0 and 1 can adjust the overall threatnumber TN to more accurately assess the risk of collision, e.g., asdescribed above, from decelerating at −6.5 m/s² to decelerating at −2.0m/s².

When the front threat number TN_(front) exceeds a predetermined threatthreshold for the first time in a turn, the computer 105 can determinethe rear brake threat number BTN_(rear). When the front threat number isbelow the threat threshold, the computer 105 can determine that the hostvehicle 101 is not likely to collide with the target 300 and can actuatecomponents 120 to continue the vehicle 101 in the turn. When the frontthreat number exceeds the threat threshold for a first time uponinitiating the turn, either the host vehicle 101 will collide with thetarget 300 or the host vehicle 101 will pass by the rear end of thetarget 300 (i.e., a false positive “near miss” scenario”). Thus, thecomputer 105 can determine the rear time to collision TTC_(rear,long),the rear lateral distance L_(rear,lat), and/or the rear brake threatnumber BTN_(rear) to determine whether the host vehicle 101 is at riskof colliding with the target 300. After determining that the frontthreat number exceeds the threat threshold for the first time uponinitiating the turn, the computer 105 can refer to the previouslydetermined overall threat number until completing the turn. Aftercompleting the turn, the computer 105 can reset the overall threatnumber until a subsequent turn.

The computer 105 can determine a rear longitudinal time to collisionTTC_(rear,long). The rear longitudinal time to collision TTC_(rear,long)is the predicted time, based on the current vehicle 101 and targetspeeds V, for the host vehicle 101 to reach the rear point 310. Thecomputer 105 can determine the rear longitudinal time to collisionTTC_(rear,long) as the time T at which the rear relative longitudinaldistance L_(rear,long)=0, i.e., solving Equation 1 for TTC_(rear,long):

$\begin{matrix}{0 = {{L_{{rear},{long}}(t)} + \frac{a_{{long},h}{{\overset{.}{\psi}}_{h}(t)}^{2}{TTC}_{{rear},{long}}^{4}}{8} + \frac{{V_{{long},h}(t)}{{\overset{.}{\psi}}_{h}(t)}^{2}{TTC}_{{rear},{long}}^{3}}{6} + {\frac{1}{2}\left( {{a_{{long},{tg}}(t)} - {a_{{long},h}(t)}} \right){TTC}_{{rear},{long}}^{2}} + {\left( {{V_{{long},{tg}}(t)} - {V_{{long},h}(t)}} \right){TTC}_{{rear},{long}}}}} & (3)\end{matrix}$The computer 105 can use conventional techniques to solve Equation 3,e.g., root-finding algorithms, Newton's method, the quartic formula,etc.

The computer 105 can determine whether the rear time to collisionTTC_(rear,long) is less than a time threshold. The time threshold can bebased on, e.g., a brake response time, simulations of collisions inintersections, resolution tolerances in data 115 collection by thesensors 110, etc. For example, the time threshold can be greater thanthe brake response time by at least one or more resolution tolerances indata 115 collection to allow the computer 105 enough time to actuate thebrake 120 to avoid and/or mitigate the collision. The time threshold canbe, e.g., 0.8 seconds. If the rear time to collision TTC_(rear,long) isless than the time threshold, the computer 105 can determine to operateaccording to the front threat number TN_(front). If the rear time tocollision TTC_(rear,long) is less than a time threshold, the computer105 can set the threat multiplier to 1.

The computer 105 can determine a rear lateral distance threshold for thehost vehicle 101. The rear lateral distance threshold can be, e.g., alateral distance between the origin O of the host vehicle 101 and anedge of the host vehicle 101, and the rear lateral distance thresholdcan be determined such that the rear point 310 is beyond the edge of thehost vehicle 101 by at least a safety margin, described below, when therear lateral distance L_(rear,lat) exceeds the rear lateral distancethreshold. As shown in FIGS. 5-6, the host vehicle 101 passes the targetvehicle 300 when:

$\begin{matrix}{{L_{{rear},{lat}}\left( {t + {TTC}_{{rear},{long}}} \right)} < {{- \frac{H_{width}}{2}} + C_{{rear},{lat}}}} & (4)\end{matrix}$where

$- \frac{H_{width}}{2}$is the coordinate in the lateral direction Y indicating the right sideof the host vehicle 101, i.e., indicating that the vehicle 101 avoidsthe rear point 310. Because the origin of the coordinate system used inthe equations is at the origin O at the center of the front bumper ofthe host vehicle 101, the rear end and right side of the host vehicle101 have negative coordinates. That is, the coordinate in thelongitudinal direction X at the rear end of the host vehicle 101 is 0,and the coordinate in the lateral direction Y at the right side of thehost vehicle 101 is

$- {\frac{H_{width}}{2}.}$The rear lateral distance threshold can be, e.g., 1 meter. A safetymargin C_(rear,lat) can be determined to increase the rear lateraldistance threshold above half the width H_(width) of the host vehicle101 to account for, e.g., tolerances in the Taylor series expansion,data collection from the sensors 110, and brake timing, etc. Thecomputer 105 can determine whether the host vehicle 101 will collidewith the target 300 based on the width of the host vehicle 101 and thesafety margin C_(rear,lat). The safety margin can be based on, e.g.,simulation data of intersections and estimated resolution tolerances ofthe sensors 110. For example, the safety margin C_(rear,lat) can betwice the resolution tolerance of the sensor 110 with the highestresolution tolerance to provide a safety factor of two. The safetymargin C_(rear,lat) allows the vehicle 101 to avoid the target 300 whileaccounting for potential variations in vehicle 101 operation.

The computer 105 can determine whether the rear lateral distanceL_(rear,lat) (t+TTC_(rear,long)) at the rear time to collisionTTC_(rear,long) is less than the rear lateral distance threshold. Thecomputer 105 can, using Equations 2-3 above with the rear time tocollision TTC_(rear,long), determine the rear lateral distanceL_(rear,lat) (t+TTC_(rear,long)). If the rear lateral distanceL_(rear,lat) is less than the rear lateral distance threshold, thecomputer 105 can set the threat multiplier to 1.

The computer 105 can determine whether the rear brake threat numberBTN_(rear) is greater than a rear threat threshold. As described above,the rear brake threat number BTN_(rear) is a measure of a neededlongitudinal deceleration to allow the host vehicle 101 to stop orreduce speed prior to colliding with the target 300. The computer 105can determine the rear brake threat number BTN_(rear) as:

$\begin{matrix}{{BTN_{rear}} = {\min\left( {{\frac{V_{h}(t)}{TT{C_{{rear},{long}}(t)}} \cdot \frac{1}{a_{{maxdecel},h}}},1} \right)}} & (5)\end{matrix}$where a_(maxdecel,h) is a maximum deceleration of the host vehicle 101.If the rear brake threat number BTN_(rear) is greater than the rearthreat threshold, as described above, the computer 105 can set thethreat multiplier to 1.

If the rear threat number TN_(rear) is below the rear threat threshold,i.e., none of threshold values described above are met, the computer 105can set the threat multiplier to 0. That is, the computer 105 candetermine that the scenario during the turn is a “near miss” and thatthe host vehicle 101 is not likely to collide with the target 300. As aresult, the computer 105 can multiply the threat multiplier to the frontthreat number TN_(front) to determine an overall threat number TN. Whenthe overall threat number TN is TN_(front), the computer 105 can actuateone or more components 120 in the turn to avoid the target 300. When theoverall threat number TN is 0, the computer 105 can actuate the steeringcomponent 120 to complete the turn.

FIG. 7 is a block diagram of an example process 700 for operating a hostvehicle 101 during a turn. The process 700 begins in a block 705, inwhich the computer 105 actuates one or more sensors 110 to collect data115 about a target 300. The computer 105 can collect data 115 about,e.g., a target 300 speed, front point 305, rear point 310, acceleration,etc.

Next, in a block 710, the computer 105 can determine a front threatnumber TN_(front). As described above, the front threat numberTN_(front) is a prediction of whether a specific target 300 willintersect or collide with the host vehicle 101 at the front point 305.The front threat number TN_(front) can be the greatest of a determinedbrake threat number BTN, acceleration threat number ATN, and/or steeringthreat number STN, as described above.

Next, in a block 715, the computer 105 determines whether the frontthreat number TN_(front) exceeds a predetermined threat threshold. Asdescribed above, when the front threat number TN_(front) exceeds thepredetermined threat threshold, the computer 105 can determine that thehost vehicle 101 is likely to collide with the target 300. The threatthreshold can be determined based on, e.g., empirical testing ofvehicles 101 in intersections, simulation modeling of vehicles 101,brake capacity, steering limits, etc. The threat threshold can be apredetermined value determined by the computer 105 and/or the server 130and stored in the data stores 106 and/or 135. For example, the server130 can use acceleration data from a plurality of vehicles 101 todetermine a maximum deceleration for the vehicles 101 and can determinethe threat threshold based on the maximum deceleration. If the frontthreat number TN_(front) exceeds the threat threshold, the process 700continues in a block 720. Otherwise, the process 700 continues in ablock 725.

In the block 720, the computer 105 determines whether the front threatnumber TN_(front) has exceeded the threat threshold for the first timeupon initiating the turn. That is, as described above, upon firstdetermining that the front threat number TN_(front) exceeds the threatthreshold, the computer 105 can determine whether the likelihood ofcollision is a false positive, i.e., a near miss, or whether to actuatecomponents 120 to avoid and/or mitigate a collision with the target 300.On subsequent determinations that the front threat number TN_(front)exceeds the threat threshold in the turn, the computer 105 refers to thethreat number determined upon first exceeding the threat threshold. Ifthe computer 105 determines that the front threat number TN_(front) hasexceeded the threat threshold for the first time upon initiating theturn, the process 700 continues in a block 730. Otherwise, the process700 continues in a block 725.

In the block 725, the computer 105 determines the overall threat numberTN. As described above, the overall threat number TN can be, e.g., apreviously determined threat number TN or the front threat numberTN_(front) multiplied by a threat multiplier. The threat multiplieradjusts the front threat number TN_(front) based on information from therear point 310. For example, if the computer 105 determines that thehost vehicle 101 is in a near miss scenario, the computer 105 can setthe threat multiplier to 0. Upon determining the overall threat numberTN, the computer 105 can actuate one or more components 120 to avoidand/or mitigate a collision.

In the block 730, the computer 105 determines a rear time to collisionTTC_(rear,long). As described above, the rear time to collisionTTC_(rear,long) predicts a time elapsed until a relative rearlongitudinal distance L_(rear,long) reaches 0, i.e., the origin O at thecenter point of the front bumper of the host vehicle 101 has 0longitudinal distance from the rear point 310.

Next, in a block 735, the computer 105 determines whether the rear timeto collision TTC_(rear,long) is below a predetermined time threshold.When the rear time to collision TTC_(rear,long) is below thepredetermined time threshold, the computer 105 can determine that thecalculations to determine the rear time to collision TTC_(long,rear) maybe affected by, e.g., tolerance errors, rounding errors, errors from theTaylor series expansion, etc., and may indicate a near miss scenario. Ifthe rear time to collision TTC_(rear,long) is below the predeterminedtime threshold, the process 700 continues in a block 740. Otherwise, theprocess 700 continues in a block 760.

In the block 740, the computer 105 determines a rear lateral distanceL_(rear,lat) at the rear time to collision TTC_(rear,long). The rearlateral distance L_(rear,lat) is the lateral distance between the centerO of the host vehicle 101 and the rear point 310 of the target 300.

Next, in a block 745, the computer 105 determines whether the rearlateral distance L_(rear,lat) is below a predetermined rear lateraldistance threshold. The rear lateral distance threshold can be, e.g., alateral distance between the origin O at the center point of the frontbumper of the host vehicle 101 and an edge of the host vehicle 101, andthe rear lateral distance threshold can be determined such that the rearpoint 310 is beyond the edge of the host vehicle 101 when the rearlateral distance L_(rear,lat) exceeds the rear lateral distancethreshold. If the rear lateral distance L_(rear,lat) is below the rearlateral distance threshold, the process 700 continues in a block 750.Otherwise, the process 700 continues in the block 760.

In the block 750, the computer 105 determines a rear threat numberTN_(rear). For example, the computer 105 can determine a rear brakethreat number BTN_(rear), as described above. The rear brake threatnumber BTN_(rear) can be a measure of a change in longitudinalacceleration to allow one of the host vehicle 101 to stop or the rearpoint 310 of the target 300 to pass the host vehicle 101.

Next, in a block 755, the computer 105 determines whether the rearthreat number TN_(rear) is below a predetermined rear threat threshold.As described above, the rear threat threshold can be determined basedon, e.g., empirical testing of vehicles 101 in intersections, simulationmodeling of vehicles 101, brake capacity, steering limits, etc. If therear threat number TN_(rear) is below the rear threat threshold, theprocess 700 continues in a block 765. Otherwise, the process 700continues in the block 760.

In the block 760, the computer 105 assigns the threat multiplier to avalue of 1. Because one of the rear time to collision TTC_(rear,long),the rear lateral distance L_(rear,lat), or the rear threat numberTN_(rear) indicates a likelihood of a collision (i.e., the scenario isnot a near miss scenario), the computer 105 assigns the threatmultiplier to 1 and actuates components 120 to avoid and/or mitigate thecollision with the target 300. By setting the threat multiplier to 1,the computer 105 actuates components 120 according to the front threatnumber TN_(front), e.g., specifying brake 120 actuation to achievedeceleration to avoid and/or mitigate the collision according to thefront threat number TN_(front). That is, the computer 105 determinesthat the risk of collision is the risk associated with the front threatnumber TN_(front) and actuates components 120 according to that amountof risk.

In the block 765, the computer 105 assigns the threat multiplier to avalue of 0. That is, the compute 105 determines that the host vehicle101 is in a near miss scenario and will not likely collide with thetarget 300. The computer 105 can actuate a steering component 120 tocomplete the turn with the overall threat number TN set to 0. In theexample process 700, the threat multiplier can be 0 or 1, but the threatmultiplier can be a different number, e.g., a number between 0 and 1, tomore finely assess the risk of collision and to provide more specificcomponent 120 actuation to avoid and/or mitigate the collision.

Next, in a block 770, the computer 105 determines whether to continuethe process 700. For example, if the host vehicle 101 is still in theturn, the computer 105 can determine to continue the process 700. Inanother example, if the host vehicle 101 has completed the turn, thecomputer can determine not to continue the process 700. If the computer105 determines to continue, the process 700 returns to the block 705 tocollect additional data 115. Otherwise, the process 700 ends.

As used herein, the adverb “substantially” modifying an adjective meansthat a shape, structure, measurement, value, calculation, etc. maydeviate from an exact described geometry, distance, measurement, value,calculation, etc., because of imperfections in materials, machining,manufacturing, data collector measurements, computations, processingtime, communications time, etc.

Computing devices discussed herein, including the computer 105 andserver 130 include processors and memories, the memories generally eachincluding instructions executable by one or more computing devices suchas those identified above, and for carrying out blocks or steps ofprocesses described above. Computer executable instructions may becompiled or interpreted from computer programs created using a varietyof programming languages and/or technologies, including, withoutlimitation, and either alone or in combination, Java™, C, C++, VisualBasic, Java Script, Perl, HTML, etc. In general, a processor (e.g., amicroprocessor) receives instructions, e.g., from a memory, a computerreadable medium, etc., and executes these instructions, therebyperforming one or more processes, including one or more of the processesdescribed herein. Such instructions and other data may be stored andtransmitted using a variety of computer readable media. A file in thecomputer 105 is generally a collection of data stored on a computerreadable medium, such as a storage medium, a random access memory, etc.

A computer readable medium includes any medium that participates inproviding data (e.g., instructions), which may be read by a computer.Such a medium may take many forms, including, but not limited to, nonvolatile media, volatile media, etc. Non volatile media include, forexample, optical or magnetic disks and other persistent memory. Volatilemedia include dynamic random access memory (DRAM), which typicallyconstitutes a main memory. Common forms of computer readable mediainclude, for example, a floppy disk, a flexible disk, hard disk,magnetic tape, any other magnetic medium, a CD ROM, DVD, any otheroptical medium, punch cards, paper tape, any other physical medium withpatterns of holes, a RAM, a PROM, an EPROM, a FLASH EEPROM, any othermemory chip or cartridge, or any other medium from which a computer canread.

With regard to the media, processes, systems, methods, etc. describedherein, it should be understood that, although the steps of suchprocesses, etc. have been described as occurring according to a certainordered sequence, such processes could be practiced with the describedsteps performed in an order other than the order described herein. Itfurther should be understood that certain steps could be performedsimultaneously, that other steps could be added, or that certain stepsdescribed herein could be omitted. For example, in the process 700, oneor more of the steps could be omitted, or the steps could be executed ina different order than shown in FIG. 7. In other words, the descriptionsof systems and/or processes herein are provided for the purpose ofillustrating certain embodiments, and should in no way be construed soas to limit the disclosed subject matter.

Accordingly, it is to be understood that the present disclosure,including the above description and the accompanying figures and belowclaims, is intended to be illustrative and not restrictive. Manyembodiments and applications other than the examples provided would beapparent to those of skill in the art upon reading the abovedescription. The scope of the invention should be determined, not withreference to the above description, but should instead be determinedwith reference to claims appended hereto and/or included in a nonprovisional patent application based hereon, along with the full scopeof equivalents to which such claims are entitled. It is anticipated andintended that future developments will occur in the arts discussedherein, and that the disclosed systems and methods will be incorporatedinto such future embodiments. In sum, it should be understood that thedisclosed subject matter is capable of modification and variation.

The article “a” modifying a noun should be understood as meaning one ormore unless stated otherwise, or context requires otherwise. The phrase“based on” encompasses being partly or entirely based on.

What is claimed is:
 1. A system, comprising a computer including aprocessor and a memory, the memory storing instructions executable bythe processor to: determine a front threat number between a turning hostvehicle and an oncoming target, the front threat number being alikelihood of a collision between the turning host vehicle and a frontpoint of the oncoming target; upon determining the front threat numberexceeds a threat threshold, determine a rear time to collision betweenthe turning host vehicle and a rear point of the oncoming target basedon a yaw rate of the turning host vehicle; upon determining that therear time to collision is below a time threshold, determine a rearthreat number for the oncoming target, the rear threat number being alikelihood of collision between the turning host vehicle and the rearpoint of the oncoming target; and actuate a component based on the rearthreat number for the oncoming target.
 2. The system of claim 1, whereinthe instructions further include instructions to determine an overallthreat number based on the rear threat number and the front threatnumber.
 3. The system of claim 2, wherein the overall threat number isbased on a threat multiplier that is based on the rear threat number. 4.The system of claim 3, wherein the instructions further includeinstructions to set the threat multiplier to zero when the rear threatnumber is below a rear threat threshold.
 5. The system of claim 1,wherein the instructions further include instructions to determine therear threat number when a predicted lateral distance from the hostvehicle to a rear corner of the oncoming target is below a distancethreshold.
 6. The system of claim 1, wherein the instructions furtherinclude instructions to determine the rear time to collision when thefront threat number exceeds the threat threshold for a first time in aturn.
 7. The system of claim 1, wherein the rear threat number is abrake threat number.
 8. The system of claim 1, wherein the instructionsfurther include instructions to actuate a steering component to completea turn when the rear threat number is below a rear threat threshold. 9.The system of claim 1, wherein the instructions further includeinstructions to determine the rear time to collision based on apredicted rear longitudinal distance.
 10. A method, comprising:determining a front threat number between a turning host vehicle and anoncoming target, the front threat number being a likelihood of acollision between the turning host vehicle and a front point of theoncoming target; upon determining the front threat number exceeds athreat threshold, determining a rear time to collision between theturning host vehicle and a rear point of the oncoming target based on ayaw rate of the turning host vehicle; upon determining that the reartime to collision is below a time threshold, determining a rear threatnumber for the oncoming target, the rear threat number being alikelihood of collision between the turning host vehicle and the rearpoint of the oncoming target; and actuating a component based on therear threat number for the oncoming target.
 11. The method of claim 10,further comprising determining a threat multiplier based on the rearthreat number.
 12. The method of claim 11, further comprising settingthe threat multiplier to 0 when the rear threat number is below a rearthreat threshold.
 13. The method of claim 10, further comprisingdetermining the rear time to collision when the front threat numberexceeds the threat threshold for a first time in a turn.
 14. A system,comprising: a brake; a steering component; means for determining a frontthreat number between a turning host vehicle and an oncoming target, thefront threat number being a likelihood of a collision between theturning host vehicle and a front point of the oncoming target; means fordetermining a rear time to collision between a turning host vehicle andan oncoming target based on a yaw rate of the turning host vehicle upondetermining a front threat number exceeds a threat threshold; means fordetermining a rear threat number for the oncoming target upondetermining that the rear time to collision is below a time threshold,the rear threat number being a likelihood of collision between theturning host vehicle and the rear point of the oncoming target; andmeans for actuating one of the brake or the steering component based onthe rear threat number for the oncoming target.
 15. The system of claim14, further comprising means for determining a threat multiplier basedon the rear threat number.
 16. The system of claim 15, furthercomprising means for setting the threat multiplier to 0 when the rearthreat number is below a rear threat threshold.
 17. The system of claim14, further comprising means for determining the rear time to collisionwhen the front threat number exceeds the threat threshold for a firsttime in a turn.